Effect of seed roasting on oxidative stability and antioxidant content of hemp seed oil

In this study, some chemical components of hemp seed, which widely consumed as snack food in Middle East were determined. The effects of different roasting temperatures (140, 160 and 180 °C) and times (0-60 min) on the oxidative stability and antioxidant content of hemp seed oil were investigated. Hemp seed oil contained high levels of linoleic acid (54.85%), α-linolenic acid (18.13%) and γ-tocopherol (707.47 mg/kg oil). While tocopherol isomers decreased with increasing roasting time and temperature, total phenolic content and antioxidant activity showed increasing trend. The peroxide and p-anisidine values of roasted samples varied from 1.33 to 3.09 meq O₂ /kg oil and 1.65 to 43.27, respectively. The peroxide and p-anisidine values of samples were simultaneously generated at the early stage of roasting. Kinetic evaluation of data showed that peroxides act as limiting factor in autocatalytic oxidation reactions. The order and rate constant regarding peroxide value were similar with those of p-anisidine value. The effects of roasting temperature and time on the oxidation parameters and antioxidant contents of samples were significant (p < 0.05). Based on peroxide and p-anisidine values, roasting at 140-160 °C for 35 min or at 180 °C for 15 min are recommended to provide good quality roasted hemp seed.